[英]Inserting records into a MySQL table using Java
我在MySQL中创建了一个包含一个表的数据库:
CREATE DATABASE iac_enrollment_system;
USE iac_enrollment_system;
CREATE TABLE course(
course_code CHAR(7),
course_desc VARCHAR(255) NOT NULL,
course_chair VARCHAR(255),
PRIMARY KEY(course_code)
);
我尝试使用Java插入记录:
// STEP 1: Import required packages
import java.sql.*;
import java.util.*;
public class SQLInsert {
// JDBC driver name and database URL
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost:3306/iac_enrollment_system";
// Database credentials
static final String USER = "root";
static final String PASS = "1234";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
Scanner scn = new Scanner(System.in);
String course_code = null, course_desc = null, course_chair = null;
try {
// STEP 2: Register JDBC driver
Class.forName("com.mysql.jdbc.Driver");
// STEP 3: Open a connection
System.out.print("\nConnecting to database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
System.out.println(" SUCCESS!\n");
// STEP 4: Ask for user input
System.out.print("Enter course code: ");
course_code = scn.nextLine();
System.out.print("Enter course description: ");
course_desc = scn.nextLine();
System.out.print("Enter course chair: ");
course_chair = scn.nextLine();
// STEP 5: Excute query
System.out.print("\nInserting records into table...");
stmt = conn.createStatement();
String sql = "INSERT INTO course " +
"VALUES (course_code, course_desc, course_chair)";
stmt.executeUpdate(sql);
System.out.println(" SUCCESS!\n");
} catch(SQLException se) {
se.printStackTrace();
} catch(Exception e) {
e.printStackTrace();
} finally {
try {
if(stmt != null)
conn.close();
} catch(SQLException se) {
}
try {
if(conn != null)
conn.close();
} catch(SQLException se) {
se.printStackTrace();
}
}
System.out.println("Thank you for your patronage!");
}
}
输出似乎成功返回:
但是当我从MySQL中选择时,插入的记录是空白的:
为什么要插入空白记录?
不,这不能工作(不是真实的数据):
String sql = "INSERT INTO course " +
"VALUES (course_code, course_desc, course_chair)";
stmt.executeUpdate(sql);
将其更改为:
String sql = "INSERT INTO course (course_code, course_desc, course_chair)" +
"VALUES (?, ?, ?)";
使用该sql创建PreparedStatment并使用index插入值:
PreparedStatement preparedStatement = conn.prepareStatement(sql);
preparedStatement.setString(1, "Test");
preparedStatement.setString(2, "Test2");
preparedStatement.setString(3, "Test3");
preparedStatement.executeUpdate();
如果您不想使用预准备语句,也可以这样做。
String sql = "INSERT INTO course(course_code,course_desc,course_chair)"+"VALUES('"+course_code+"','"+course_desc+"','"+course_chair+"');"
为什么它没有插入值是因为您没有提供值,但是您提供了已使用的变量的名称。
你的insert语句中有一个错误,请将其变为下面并尝试: String sql = "insert into table_name values ('" + Col1 +"','" + Col2 + "','" + Col3 + "')";
这适用于任何表,而不是对列进行硬编码。
//Source details String sourceUrl = "jdbc:oracle:thin:@//server:1521/db"; String sourceUserName = "src"; String sourcePassword = "***"; // Destination details String destinationUserName = "dest"; String destinationPassword = "***"; String destinationUrl = "jdbc:mysql://server:3306/db"; Connection srcConnection = getSourceConnection(sourceUrl, sourceUserName, sourcePassword); Connection destConnection = getDestinationConnection(destinationUrl, destinationUserName, destinationPassword); PreparedStatement sourceStatement = srcConnection.prepareStatement("SELECT * FROM src_table "); ResultSet rs = sourceStatement.executeQuery(); rs.setFetchSize(1000); // not needed ResultSetMetaData meta = rs.getMetaData(); List<String> columns = new ArrayList<>(); for (int i = 1; i <= meta.getColumnCount(); i++) columns.add(meta.getColumnName(i)); try (PreparedStatement destStatement = destConnection.prepareStatement( "INSERT INTO dest_table (" + columns.stream().collect(Collectors.joining(", ")) + ") VALUES (" + columns.stream().map(c -> "?").collect(Collectors.joining(", ")) + ")" ) ) { int count = 0; while (rs.next()) { for (int i = 1; i <= meta.getColumnCount(); i++) { destStatement.setObject(i, rs.getObject(i)); } destStatement.addBatch(); count++; } destStatement.executeBatch(); // you will see all the rows in dest once this statement is executed System.out.println("done " + count); }
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